Method of producing metal packages

ABSTRACT

A method for producing metal packages is disclosed, comprising the steps of forming a metal package, in particular from steel or aluminum, from a sheet metal material, in particular from thin or very thin sheet or tin plate, wherein the metal package comprises a cavity having inner surfaces that are coated with a paraffin-based coating material. The coating material is preferably heated after coating to a temperature above the solidifying temperature.

CROSSREFERENCES TO RELATED APPLICATIONS

This application is a continuation of international patent applicationPCT/EP2010/061732, filed on Aug. 12, 2010 designating the U.S., whichinternational patent application has been published in German languageand claims priority from German patent application 10 2009 038 129.2,filed on Aug. 12, 2009. The entire contents of these applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a method for producing metal packages frommetal sheets with a coating and to metal packages of sheet material, inparticular of thin or very thin sheet or tin plate, for receiving in aninterior space a product with which they are filled.

Such metal packages are known in principle in the prior art and are soldby the applicant in various forms including those of flat-top drums,canisters, seamed-lid cans, hobbocks and barrels.

Such metal packages are used for packaging and storingchemical/technical products, foodstuffs and, in particular, beverages.They are produced by means of methods that are generally known in theprior art, including separating and reforming processes. Connections arethereby created by various operations including that of seaming, withpreviously flanged edge regions of metal sheets being connected to oneanother by folding them over.

The known metal packages make it possible for the aforementionedproducts with which they are filled to be received in a mechanicallystable container in such a way that they are protected from light andsealed. The sealing extends here to liquid, gaseous and gas-tightconstituents of the products, and similarly undesired permeation throughthe packaging material is avoided. In addition, such containers aresuitable for receiving pressurized products. Metal packages are almostcompletely recyclable, it being possible to obtain a virtually closedmaterial cycle for the packaging materials if they are consistentlyrecovered and reused.

To ensure that the containers are resistant to corrosion, acid andgeneral media, it is necessary to provide their surfaces, in particularalso the inner sides, with a protective coating. This coating may be,for example, a combination of a metallic layer, for example a tincoating in the case of tin sheet, and an organic coating applied on top,such as for example a lacquering or an applied film. Such coatings aregenerally applied before the reforming operation to the semifinishedproduct, flat material, plate material or metal strip.

It has been found that the operations for reforming the startingmaterial that follow in the course of the production of the metalpackage, such as for example drawing, flanging or seaming operations,can impair the protective effect of a lacquer layer particularly. Forthis reason there has been a change in the practice employed, toalternatively or additionally coating the interior space of a completedor semifinished metal package with lacquers by an internal sprayingmethod. However, it must be noted here that the internal spraying methoddoes not allow the lacquer layer to be applied to all the componentparts of the package, such as for example in the case of interior spacesin a package with areas that are difficult to access or with very smallfilling openings.

In the course of the subsequent application of lacquers, it is necessaryfor the coating to be followed by a drying operation. This involves thelacquer layer being dried or baked at a greatly increased temperature,for instance at 180 to 200° C., which is applied for a considerable timeperiod, for example approximately 12 minutes. This high thermal loadingnecessarily requires more complex equipment and greater expenditure onthe supply of energy and the disposal of emissions, such as for exampleof degasifying and evaporating matter. Furthermore, such treatment maycause the risk of a coating, printing or lacquering of the outer side ofthe package being damaged.

SUMMARY OF THE INVENTION

In view of this, it is a first object of the invention to disclose amethod of producing metal packages allowing for improved corrosionprotection.

It is a second object of the invention to disclose a method of producingmetal packages that renders possible a relatively simple production.

It is a third object of the invention to disclose a metal package thathas increased corrosion protection.

According to one aspect these or other objects are solved by a methodcomprising the steps of:

-   -   providing a metal package made of sheet metal and having a        cavity formed by inner surfaces;

providing a paraffin-based coating material;

heating said coating material to a temperature above a solidifyingtemperature thereof;

applying said coating material onto said inner surfaces of said cavity;

solidifying said coating material; and

cooling said metal package to room temperature.

With respect to a material package of the type mentioned at the outset,the object of the invention is achieved in that at least the interiorspace of the package has a surface coating comprising a paraffin-basedcoating agent.

The object of the invention is completely achieved in this way.

This is so because, according to the invention, a metal package isformed and then its interior space is coated with a paraffin-basedcoating agent, so as to obtain an organic coating which ensuresexcellent corrosion protection and is not subjected to any subsequentmechanical deformation or damage caused by reforming processes in theproduction of the metal package. In this way, a high integrity of thecoating can be ensured.

One particular advantage of the solution according to the invention isthat a greatly reduced porosity is achieved in comparison with spraylacquered coatings. Consequently, corrosion currents can in principle beminimized or prevented, which leads to much improved corrosionprotection. Accordingly, it may also be possible for a package accordingto the invention to be successfully filled with aggressive products,which for instance contain acids or lyes.

Paraffinic hydrocarbons are non-toxic and are not considered to be ahealth hazard, and so they can certainly come into consideration for usein packages for foodstuffs or beverages. In addition, on account oftheir non-reactivity, paraffins are outstandingly suitable as corrosionprotection agents; they are, in particular, not water-soluble and arevery resistant to many kinds of acids. Consequently, they areparticularly suitable for use in metal packages for carbonatedbeverages, such as for example beer or cola.

For the purposes of this application, the paraffin-based coating agentshould be understood as meaning a substantially paraffin-containingcoating agent which advantageously consists of paraffin to over 75%,preferably to over 85% and more preferably to over 95%. The coatingagent may be supplemented by adding fillers, solvents, dyes, binders andother additional substances, for example fats and natural or syntheticwaxes, or else by additions of production-related residual constituents,such as for example oil residues.

It is conceivable for the coating agent to consist completely or almostcompletely of paraffin. In this way it can be ensured that no, or onlyinsignificant, constituents of the coating agent are released aftercoating by degassing or dissolving.

It should be noted in this connection that paraffins should beunderstood as meaning substantially paraffinic hydrocarbons, whichgenerally have a low reaction tendency. Paraffins may be composed ofunbranched (n-) and branched (iso-) alkanes, the reason for theiradvantageous properties. Paraffinic hydrocarbons are substantiallywax-like, odorless and tasteless, electrically nonconducting andhydrophobic.

Depending on their chain structure, paraffins may be classifiedaccording to their viscosity and their solidifying temperature. Thisapplication is primarily, but not exclusively, intended to focus onmixtures with particularly long-chain hydrocarbons. Furthermore,paraffins should also be understood as including what are known as microwaxes.

According to a development of the invention, the coating agent isapplied under pressure, in particular by the airless spraying method.

In this way it is made possible to apply the coating agent by means ofknown techniques. A uniform initial coating is obtained. The airlessspraying method is particularly suitable for applying the coating agent,since, by contrast with air-pressure-based spraying methods, the coatingagent is applied here without an additional carrier medium. This allowscontamination of the metal package or the coating agent withconstituents of the process air that occur in a method with compressedair to be avoided. Similarly, there is no need for laboriouspreparation, cleaning or filtering of the process air. In an alternativerefinement of the invention, the coating agent is applied by means of apouring or sprinkling method.

This measure allows the coating agent to be applied without pressure.Consequently, the complexity of the production and equipment is reduced.It is also possible here to dispense with the use of process air forapplying the coating agent, so that contamination of the metal packageand of the coating agent can be reduced, thereby increasing the qualityof production and the reliability of the process.

Applying the coating agent by gravitational force by means of pouring orsprinkling methods can similarly ensure influencing of the layerthickness to be achieved. By variation of various parameters, such asfor example the viscosity of the coating agent, the temperature of thecoating agent or of the metal package to be coated or else the surfacefinish of the interior space of the metal package, a desired layerthickness can be set.

In an advantageous development of the invention, for coating, thecoating agent is heated to a temperature above the solidifyingtemperature.

This measure makes it possible to process paraffin-based coating agentswithout the addition of solvents. In this way, only local areas of theproduction plant have to be heated, thus promoting rapid adhering andsolidifying of the coating agent on the metal package not heated by theplant. It is conceivable to heat the coating agent directly in a storagecontainer or reservoir or else to achieve the introduction of heat intothe coating agent indirectly by heating up parts of the coating device.

In a preferred development of the invention, the coating agent has asolidifying temperature of over 70° C., preferably of over 85° C., morepreferably of over 90° C.

Such high solidifying temperatures can be advantageously achieved withmicro waxes. In this way, a sufficiently high thermal stability of theapplied coating for the further processing, filling with the product andlater use can be ensured.

Furthermore, the solidifying temperatures are still chosen low enough tokeep down the energy requirement for heating the coating agent, andconsequently restrict the complexity of the production and theproduction plants. Furthermore, protection of the outer surface of themetal package from high thermal loads is ensured. This allows alacquering, printing or coating that is applied to the outside of thecontainer to be applied already before the sheet-reforming operation, onthe flat semifinished product, without being damaged by such thermalloads.

It is particularly preferred to heat the coating agent after coatingonce again to a temperature above the solidifying temperature.

In this way, the applied, already partially or completely solidifiedcoating agent can be partly or fully melted in order to wet the interiorspace of the metal container completely with the again liquefied orviscous paraffin. This allows wetting of even inaccessible areas inwhich initial application of the coating agent could not take place. Inaddition, the integrity and homogeneity of the coating agent and thesurface of the coating agent can be improved, since the liquid orviscous coating agent is capable of filling or healing microcracks onits surface or gaps in the application.

For this purpose, the applied coating agent is preferably brought to atemperature of approximately 100° C. and kept at this temperature forapproximately two to three minutes. This can greatly simplify theproduction process and improve the corrosion protection, since possibledefects and cracks in the initial layer can be closed or healed in adependable way by a subsequent production step.

In an advantageous development of the invention, during the forming ofthe metal package there is formed at least one folded seam connection,which is coated with the coating agent during the subsequent coating ofthe interior space.

In this way it has been made possible to use reforming and joiningprocesses that are simple, inexpensive and suitable for mass productionto form the metal package, since it can be ensured by the coating with aparaffin-based coating agent that even areas that are particularlydifficult to access, such as for example seaming channels, can becovered with the coating agent.

In an advantageous development of the invention, for applying orreheating the coating agent, the metal package is arranged such that itis aligned so as to completely wet the interior space with the coatingagent.

Consequently, with suitable alignment, the applied liquid or viscouscoating agent can, under the influence of gravitational force, penetrateof its own accord into areas of the metal package that are difficult toaccess, such as for example folded seam connections, in order to ensurecomplete coating of the interior space. It is conceivable to align themetal package a number of times during production, and in this wayfurther increase the reliability of the process in terms of the coatingoperation, and similarly thereby allow areas that are particularlydifficult to access to be wetted with the coating agent.

For example, in the course of alignment the metal package may be turnedby 180 degrees, in order after complete covering of the bottom area ofthe metal package to then cover the area opposite that dependably withthe coating agent. When doing so, any opening there may be in the lidmay be suitably closed. It is alternatively conceivable in the course ofthe coating process to allow excess coating agent to run out of themetal package simply under the effect of gravitational force after ithas been suitably aligned.

In a preferred development of the invention, when applying or re-heatingthe coating agent, the metal package is pivoted so as to completely wetthe interior space with the partly or fully melted coating agent.

By means of a continuous pivoting movement, it can be achieved in thisway that the coating agent is applied particularly dependably andquickly to the entire interior space of the metal package.

The pivoting movement may take place already during the initialapplication of the coating agent, but similarly in the course ofpossible subsequent follow-up steps of heating the applied coating.

According to a development of the invention, the coating agent is mixedwith a solvent for paraffin.

This can bring about the effect that the viscosity of the coating agentand the processing temperature for applying the coating agent arelowered. This allows energy savings to be achieved, since the coatingagent does not first have to be brought to a higher processingtemperature. Furthermore, by adding solvents to the coating agent,further process-relevant properties can be suitably influenced. It isconceivable for the creep of the coating agent or the adhesion on thespecific sheet material to be improved.

It goes without saying that non-toxic and unharmful solvents shouldpreferably be used. It is alternatively conceivable for it to bepossible to use other solvents that have an outstanding dissolvingeffect in the case of paraffins, such as for example benzene, ether andchloroform. It also goes without saying that the solvents should escapecompletely after application, after which the coating agent can have theadvantageous properties of almost pure or completely pure paraffin.

It should be noted in this connection that the proportion of paraffin inthe coating agent may be altered by constituents undergoing degassing orother releasing processes, in any event may be greater after theproduction of the metal package than before the application of thecoating agent.

It goes without saying that the features of the invention mentionedabove and still to be explained below can be used not only in therespectively specified combination but also in other combinations or ontheir own without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention emerge from thefollowing description of a number of preferred exemplary embodimentswith reference to the drawings, in which:

FIG. 1 shows a perspective representation of a partially cut-open metalpackage according to the invention in the form of a barrel;

FIG. 2 shows a perspective view of a further metal package according tothe invention in the form of a can;

FIG. 3 shows a perspective representation of a further metal packageaccording to the invention in the form of a canister;

FIG. 4 shows a section through a metal package according to theinvention with a seamed lid;

FIG. 5 shows a schematic representation of an installation for coatingthe interior space of a metal package using the method according to theinvention;

FIG. 6 shows a view of a nozzle for use in the method according to theinvention;

FIG. 7 shows a partial section of an embodiment of a nozzle that hasbeen modified in comparison with FIG. 6;

FIG. 8 shows a schematic partial view of an embodiment of aninstallation for coating a metal container that has been modified incomparison with FIG. 5;

FIG. 9 shows an enlarged partial section through a metal packageaccording to the invention in the area of a folded seam connection withan applied coating agent;

FIG. 10 shows a view according to FIG. 9 with an interior space of themetal container that has been completely wetted by a partly orcompletely melted coating agent; and

FIG. 11 shows a schematic representation of a pivoting device forpivoting or aligning a metal container according to the invention whencarrying out the method according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1, a metal package according to the invention in the form of abarrel is represented and denoted as a whole by 10.

Such metal packages are widely used for packaging and storing chemicalor technical products or else foodstuffs, in particular beverages.Packages of such a design have found widespread use as beer barrels. Ingeneral, such beer barrels have a filling volume from approximatelythree to approximately twenty liters, barrels known as 5-liter partybarrels having become established as a common container size. However,barrels with a filling volume from just a few liters to several hundredliters are offered primarily for wholesale demand and for chemical ortechnical products.

Metal packages of such a design are usually formed from thin or verythin metal sheets. Usually, very thin sheets have thicknesses of lessthan 0.5 millimeter, while thin sheets cover approximately the thicknessrange from 0.5 to 3 millimeters. Materials and semifinished products forproducing such metal packages are flat strips, plates and coils of tinplate, non-tin plate or else special electrolytically chrome-coatedsteel sheet.

The metal package 10 shown in FIG. 1 is fashioned from the flat materialby various re-forming and joining operations. The metal package 10 has ashell element 15, which surrounds an interior space 12 and is connectedin its lower area to a bottom element 11 and in its upper area to a lidelement 13 by means of folded seam connections 17. The lid element 13has a filling opening 16, for example for filling with beer. The bottomelement 11 and the lid element 13 may be formed, for example, frompre-punched round blanks. The shell element 15 is formed from flatstrip, the cylindrical form being produced by bending over and joiningtwo ends of the substantially rectangular starting material by means ofa folded seam connection (not represented). It is alternativelyconceivable to form the shell element 15 from a tubular semifinishedproduct.

A metal package according to the invention may well have in addition tothe filling opening 16 further openings, such as for example forintegrating a tap cock or for aerating or venting.

In the course of shaping such a container, many separating, joining orreforming processes may be used, such as in particular punching,cutting, expanding, flanging, seaming, welding or beading.

It should be noted in this connection that the term “metal package” mustnot be understood as implying that the finished package or the filledcontainer does not have any non-metal component parts. It is normal andconceivable to provide plastic-based closures, valves or transportingaids, such as handles or edge protectors, and so “metal package” shouldnot be understood restrictively in this respect.

FIG. 2 shows a further metal package 10 a according to the invention. Bycontrast with the metal package 10 that is represented in FIG. 1, themetal package 10 a in FIG. 2 is represented in a one-part state. Theshell element 15 may be formed by expanding or deep-drawing a flat orpreformed semifinished product. The form of container that is shown inFIG. 2 usually serves for receiving carbonated beverages, in particularbeer or cola, but is also used for filling with other products. Suchpackages, known in the form of beverage cans, may be made of theaforementioned steel sheets, alternatively of aluminum sheets, but alsoof a combination of metal material. Widely used filling capacities arefor instance 0.2, 0.25, 0.33, 0.5, 0.75, 1.0 and 1.5 liters.

The usual form of a beer or cola can with a metal single-use closuregives rise to a special technical feature in terms of production orfilling; that is that a lid element (not represented in FIG. 2) is onlyconnected to the shell element 15 after the product has been introducedthrough the filling element 15 of the metal package 10 a.

A further modified embodiment of a metal package according to theinvention is shown in FIG. 3 and is denoted by 10 b. The metal package10 b in the form of a canister may serve for receiving liquid chemicalproducts, such as for example paint or varnishes, but also for storingfree-flowing granules or powder. In the foodstuffs sector, suchcontainers are used for applications including the storing of edibleoil.

In a configuration given by way of example, the metal package 10 b has ashell element 15, which also bounds the bottom area of the metal package10 b, so that all that is additionally provided is a lid element 13,which is connected to the shell element 15 by way of a folded seamconnection 17. In an alternative refinement, such a canister may alsohave an additional folded seam connection for receiving a bottomelement, for instance by analogy with FIG. 1.

In FIG. 4, a further metal package 10 c is represented. The sectionalview clearly shows the configuration of the folded seam connection 17for connecting the lid element 13 to the shell element 15. It isimmediately evident that, to fashion such a folded seam connection inthe case of the shell element 15 and the lid element 13, flanging orseaming operations must be performed, whereby the individual metalsheets are subjected to high degrees of re-forming in these areas.

It should once again be pointed out that it is known in the prior art toprovide the sheets that are used with coatings, such as for exampledecorative lacquerings or printings or corrosion protection agents,either in the flat state before the re-forming or else in the re-formedor joined state. In the areas of the sheets that have high degrees ofre-forming, these coatings may be weakened or damaged by theseoperations if they are applied before the re-forming or joining.

This disadvantage can be obviated by alternative or additional coatingof the metal package, in particular of the interior space of the metalpackage, after the reforming and joining, although this increases thecomplexity of the production and may give rise to other disadvantages.For example, it is known that with the drying of a coating or lacqueringapplied to the interior space 12 of the metal package 10 c, which in thecase of conventional lacquers is performed at high temperatures ofapproximately 180 to 200° C., a decorative lacquering applied on theouter side 18 of the metal package 10 c may be impaired or damaged bydiscolorations or the like.

Alternatively, by omitting this additional inner coating, a reducedcorrosion protection would have to be accepted in the interior space 12of the metal container 10 c, and there in particular in the area inwhich individual elements come together to form a folded seamconnection.

To avoid such disadvantages, it is thus proposed according to theinvention to apply a coating with a paraffin-based coating agent in theinterior space of a metal package.

FIG. 5 shows a schematic representation of an installation for carryingout the method according to the invention.

A metal package 10, represented in a simplified state and formed forinstance according to FIGS. 1 to 4 is arranged in relation to a coatingdevice denoted by 20. Here it is conceivable for the feeding movementand further possible relative movements of the metal package 10 withrespect to the coating device 20 to be produced by a handling devicethat is schematically represented in FIG. 5 and denoted as a whole by40. The handling device may have lifting means or turning means, asindicated by the arrows 46 and 44, respectively, in order to move themetal package 10 in relation to a nozzle part 24.

Alternatively, it is conceivable to move the coating device 20, or atleast a feeding means 22 assigned thereto and having the nozzle part 24,in relation to the metal package, which will be explained in more detaillater with reference to FIG. 8.

The feeding element 22 serves for supplying the nozzle 24 with thecoating agent 30. Provided for this purpose are lines 28, configured inFIG. 5 by way of example as a ring line. It goes without saying that thefeeding element 22 may have a valve suitable for controlling the coatingoperation (not represented). The line 28 connects a container means 34,which serves for receiving a supply of the coating agent 30, to thenozzle part 24, it being possible for excess coating agent that is notapplied to be introduced once again into the container means by way of areturn. A pump 35 in the line 28 serves for generating the pressure forapplying the coating agent 30.

Before being applied, the coating agent 30 is advantageously heated orliquefied by means of heating devices 32 or 32 a. The heating device 32may serve for heating the coating agent 30 when it flows through theline 28. Additionally shown is a heating device 32 a, which serves thepurpose of heating the coating agent 30 located in the container means34, so that the target temperature of the coating agent 30 canalternatively be ensured by permanent circulation in the line 28 bymeans of the pump 35.

In FIGS. 6 and 7, design developments of the feeding means 22 arerepresented. Here, the nozzle part 24 a in FIG. 6 has a spherical shape,thereby ensuring that virtually the entire space surrounding the nozzlepart 24 a can be wetted with a coating agent.

On the other hand, in FIG. 7 the nozzle part 24 b is additionallyprovided with a joint 26, which makes it possible for the nozzle part 24b to be additionally pivoted, in order to be able to coat areas of ametal package that are difficult to access.

According to the arrangement in FIG. 5, it is sufficient to move themetal package 10 in an axis 46 in relation to the nozzle part 24 inorder to be able to achieve complete wetting of the interior space 12 ofthe metal package 10. A rotation 44 may be additionally introduced inorder to bring about a uniform distribution of the coating agent 30 overthe circumference of the interior space 12 of the metal package 10.

By contrast with this, schematically represented in FIG. 8 is a metalpackage 10 which has only a relatively small filling opening 16. Thismay make it more difficult in particular to coat corner areas of theinterior space 12 of the metal package 10. This is so particularly whena directed nozzle part 24 is used, for instance a nozzle with anemission angle of only 90 degrees or 180 degrees.

To overcome such disadvantages, in FIG. 8 there is provided analternative handling device 40 a, which serves for advancing a feedingmeans 22 a with the nozzle part 24 into the interior space 12 of themetal package 10. The handling device 40 a may have lifting means orturning means, as indicated by the arrows 46 a and 44 a, respectively.In this way, the feeding means 22 a can be introduced into the interiorspace 12 and also moved there. For the fine alignment of the nozzle part34, further joints 26 a, 26 b are provided. By combining the handlingdevice 40 a with the feeding means 22 a it is thus possible to wetalmost the entire interior space 12 of the metal package 10.

A particularly advantageous method step is then illustrated in FIGS. 9and 10.

An area of a folded seam connection 17 between a bottom element 11 and ashell element 15 of a metal package is respectively shown in section inthese figures. This detail may be representative of areas of furtherfolded seam connections, more generally of areas of a metal package thatare difficult to access. These may also be, in particular, lid seams orlateral vertical seams and any areas that are not wetted in the courseof the initial coating.

The initially applied coating agent 30′ is shown in FIG. 9. It can beseen here that the area in which the shell element 15 and the bottomelement 11 come together to go into a folded seam connection, known as aseaming channel 19, is possibly not covered completely by the coatingagent on account of its narrowness and depth. However, the coating agent30′ according to the invention can be partly or fully meltedparticularly easily at relatively low temperatures by suitably supplyingheat, indicated by 38. For this purpose, a melting device 36 is thusused for generating the heat input 38. The heat input 38 mayadvantageously take place by way of convection, heat conduction and byway of radiation into or around the metal package, for example by meansof circulation of heated air or else by infrared radiation, inparticular near infrared radiation. It is particularly advantageous interms of production to make the coating agent 30′ that is to be heatedmelt partly or fully indirectly by heating metal sheet material 14 inthe shell element 15 or the bottom element 11.

It should especially be mentioned in this connection that thetemperatures thereby occurring on the outer side of the metal packageare much lower than the temperatures during the drying of conventionallacquers on the inner side of the metal package. This dependably avoidsinstances of damage, such as for example deviations in color, of thecoating of the outer side of the package.

FIG. 10 then illustrates the desired state aimed for, in which thecoating agent then denoted by 30″ has penetrated of its own accord intothe seaming channel 19 and completely wetted it. Dependable corrosionprotection and later separation of the product from the sheet metalmaterial 14 of the metal package 10 is consequently also ensured in thisarea. The partly or fully melted coating agent 30″ is sufficientlyviscous to ensure that, in spite of running of its own accord under theeffect of gravitational force, areas once wetted are not exposed again.

This particularly preferred method step is also suitable in particularfor dependably coating inaccessible areas on outer sides of metalpackages. These may be, for example, pronounced depressions, beads orouter seam geometries. As is known, metal containers tend to corrodespecifically in such areas.

In order to assist penetration of the coating agent into areas of theinterior space of the metal package that are difficult to access, ormake it possible in the first place, it is particularly advantageous toalign or pivot the metal package suitably, so that the entire interiorarea can also actually be wetted by means of gravitationally inducedflowing.

FIG. 11 schematically shows a pivoting device suitable for this, whichis denoted as a whole by 42. The pivoting device 42 is provided withvarious pivoting or turning axes 52, 54, 56 and 58. Also provided aregripping means 50, to allow the metal package 10 to be gripped and held.By means of the pivoting device 42, the metal package 10 can then besuitably aligned or pivoted in order to direct or help the flowing ofthe coating agent. This pivoting or aligning may be performed bothdiscretely and continuously. It is thus conceivable to move the metalpackage 10 already during the heating of the applied coating agent insuch a suitable way as to keep the process time short.

As an example of discrete alignment of a metal package 10, it isconceivable to heat a container, for instance according to FIG. 1, afterthe initial application of coating agent in a position in which thebottom element 11 is on the ground, so that the coating agent canpenetrate of its own accord into the seaming channel of the folded seamconnection 17 between the bottom element 11 and the shell element 15.After that, the metal package 10 may simply be turned by 180 degrees, sothat the coating agent 30, which is still in the partly or fully meltedstate, or is brought once again into this state by re-heating, can alsopenetrate into the seaming channel between the lid element 13 and theshell element 15. When doing so, the inlet opening 16 may be suitablyclosed, in order to avoid flowing out of the molten coating agent 30.

It is similarly conceivable to introduce a greater amount of coatingagent into a metal package, deliberately allow it to flow around in theinterior space of the metal package and subsequently pour out of themetal package an excess amount of the coating agent that is notrequired.

It goes without saying that the handling, pivoting and feeding devicesshown can be suitably combined, reduced and simplified in order to makethe plant for carrying out the method according to the invention assimple and inexpensive as possible and allow it to be integrated in theestablished production sequence in the production of metal containers.

It has been accomplished within the scope of the invention to provide aparticularly simple and effective method for producing metal packages inwhich, in particular, corrosion protection in the interior space of themetal packages is ensured to an improved extent with at the same timeless complex production and at the same time improved productionquality.

A metal package according to the invention accordingly ensures highcorrosion protection along with a simplified way in which it can beproduced, particularly also meeting the requirements for suitability forfood contact applications.

1. A method of producing a metal package, comprising the steps of:providing a metal package made of sheet metal and having a cavity formedby inner surfaces; providing a paraffin-based coating material; heatingsaid coating material to a temperature above a solidifying temperaturethereof; applying said coating material under pressure by airlessspraying onto said inner surfaces of said cavity; solidifying saidcoating material; re-heating said metal package to a temperature abovesaid solidifying temperature of said coating material; and cooling saidmetal package to room temperature; wherein said metal package is pivotedat least during said step of applying said coating material or said stepof re-heating said metal package.
 2. The method of claim 1, wherein saidparaffin-based coating material comprises at least 85% of paraffin. 3.The method of claim 1, wherein said paraffin-based coating materialcomprises at least 95% of paraffin.
 4. The method of claim 1, whereinsaid metal package is made from a material selected from the groupconsisting of steel sheet metal and tin plate metal.
 5. The method ofclaim 1, wherein said container after said application step is turnedupside down for pouring out excess coating material by gravityassistance.
 6. The method of claim 1, wherein a coating material is usedhaving a solidifying temperature of more than 90° C.
 7. The method ofclaim 1, wherein said step of providing a metal package furthercomprises at least one seaming step for forming a folded seamconnection, wherein said folded seam connection is completely coatedwith said coating material during a subsequent step of applying saidcoating material onto said inner surfaces of said cavity.
 8. The methodof claim 1, wherein said inner surfaces of said cavity are fully wettedat least during one step selected form said step of applying saidcoating material and said step of re-heating said coating material. 9.The method of any of claim 1, wherein said coating material, beforebeing applied onto said inner surfaces of said cavity, is mixed with asolvent for paraffin.
 10. A method of producing a metal package,comprising the steps of: providing a metal package made of sheet metaland having a cavity formed by inner surfaces; providing a paraffin-basedcoating material; heating said coating material to a temperature above asolidifying temperature thereof; applying said coating material ontosaid inner surfaces of said cavity; solidifying said coating material;and cooling said metal package to room temperature.
 11. The method ofclaim 10, wherein said coating material is applied under pressure. 12.The method of claim 11, wherein said coating material is applied by anairless spraying method.
 13. The method of claim 10, wherein saidcoating material is applied by means of pouring or sprinkling.
 14. Themethod of claim 10, further comprising the step of pivoting said metalpackage during said step of applying said coating material.
 15. Themethod of claim 10, further comprising the step of pivoting said metalpackage during said step of re-heating said coating material.
 16. Themethod of claim 10, wherein said step of providing a metal packagefurther comprises at least one seaming step for forming a folded seamconnection, wherein said folded seam connection is coated with saidcoating material during a subsequent step of applying said coatingmaterial onto said inner surfaces of said cavity.
 17. The method of anyof claim 10, wherein said coating material is mixed with a solvent forparaffin.
 18. The method of claim 10, wherein said container after saidapplication step is turned upside down for pouring out excess coatingmaterial by gravity assistance.
 19. A metal package of a sheet metalmaterial comprising a cavity having inner surfaces which are completelycovered by a paraffin-based coating material.
 20. The metal package ofclaim 19, in which said inner surfaces comprise a shell element and atleast one bottom or lid element, wherein at least said bottom element orlid element is connected to said shell element by a folded seamconnection which is covered by said paraffin-based coating material.